Conventionally, as disclosed in Patent Document 1, a display device, such as a radar device, has been known, which has a function to display a VRM (Variable Range Marker) and an EBL (Electronic Bearing Line) on a display screen. The VRM is a range ring used for measuring a distance to an object on the display screen, and an operator can grasp a distance from a ship to an observed position by referring to the VRM. The EBL is an azimuth line used for measuring an azimuth of the object on the display screen, and the user can grasp the azimuth of the observed position seen from the ship by referring to the EBL.
Moreover, with a display device for displaying a nautical chart and the like, in a case of displaying a distance and azimuths between two positions, an operator first uses a cursor key, a trackball or the like to move a pointer, and selects a single position (reference position) on the nautical chart. Next, the operator performs operation of shifting to a mode in which the distance and the like are displayed. When the pointer is moved after the mode shifting, for example, the distance from the reference position to the position of the pointer and the azimuth of the position of the pointer seen from the reference position are displayed on the display screen.